In my U.S. Pat. No. 4,185,191, issued Jan. 22, 1980 entitled "Range Determination System" assigned to the Assignee of the present invention, I disclosed an invention for use in autofocus cameras, to determine the range to a remote object by the use of pairs of detectors mounted in a row behind a corresponding row of small lenslets which receive light from the remote object through the taking lens of the camera. Each of the detector pairs receives an image of the exit pupil of the taking lens, and if the object is in proper focus, the amount of radiation received by each detector in the pair will be approximately the same. If the object is not in focus, then the amount of radiation received by the detectors will not be the same, and by analyzing the outputs of the individual detectors in each pair, a pair of curves may be generated, the relative displacement of which is indicative of the range to the object which information may be used to, for example, automatically focus a camera.
In my co-pending application Ser. No. 282,379, filed July 13, 1981, entitled "Two Dimensional Image Panel With Range Measurement Capability," now U.S. Pat. No. 4,410,804, issued Oct. 18, 1983 and assigned to the assignee of the present invention, I disclosed an apparatus which uses the detectors of the above-mentioned patent 4,185,191 in connection with an array that can enable the user to determine not only the range to an object but also simple pattern recognition to identify the object. Such apparatus is intended for use, for example, on industrial robots to measure the distance to an object, and determine its identity so as to move a robot arm in a controlled manner.
The system of the above-mentioned U.S. Pat. No. 4,185,191 requires that there be a certain amount of subject contrast in order to perform accurate distance measurement. There are, however, situations where it is desirable to detect and measure rather featureless objects or surfaces which do not have sufficient contrast. Accordingly, the passive system of the abovementioned U.S. Pat. No. 4,185,191 is not able to accurately determine the distance to the object and the camera or the robot arm cannot be controlled in the desired manner.
In the art of range determination there are, however, "active" systems which do not require object contrast. One such system is shown in my U.S. Pat. No. 4,317,991, issued Mar. 2, 1982, entitled "Digital Autofocus System Utilizing a Photodetector Array" and assigned to the Assignee of the present invention. In this "active" autofocus system, a beam of modulated energy is projected towards the object and the energy reflected therefrom is directed through special optics to a special detector array. By determining the position of the reflected energy on the detector array, the distance to the object is obtained. Many other "active" systems are known, some of which utilize sonic energy and time the travel of a pulse from the source to the object and back as a measure of distance and some of which utilize light energy in the visible or infrared regions with various detection arrangements to provide a distance measurement by triangulation. Such systems do not depend on object contrast for their range determining abilities. When using "active" systems, however, the features of the object cannot be determined and accordingly, such systems cannot be used for object recognization. None of the prior art systems either active or passive can be used for recognition of an object and also for range determination of a low contrast or featureless surface with the same set of detector elements.